Titanium catalysts which comprise a solid titanium catalyst component containing magnesium, titanium, halogen, and if necessary, an electron donor, and an organic aluminum compound, and vanadium catalysts which comprise a vanadium compound and an organic aluminum compound, have conventionally been known as catalysts for producing olefin polymers such as ethylene polymers, propylene polymers, ethylene-.alpha.-olefin copolymers, etc. Also, Ziegler catalysts comprising a metallocene compound such as zirconocene, and an organic aluminum oxycompound (aluminoxane), have been known as catalysts that can be used to manufacture olefin polymers with a high polymerization activity. Furthermore, olefin polymerization catalysts comprising a nickel compound or a palladium compound and a cocatalyst such as aluminoxane, an ionic compound, etc., have been proposed recently as new olefin polymerization catalysts (J. Am. Chem. Soc. 1995, 117, 6414-6415).
Ethylene polymers, propylene polymers, and other olefin polymers are used as molding materials for various needs due to their excellent properties such as mechanical strength, heat resistance, transparency, chemical resistance, etc. Such olefin polymers are thus required to have good molding properties (moldability).
However, though the above-mentioned catalysts comprising a nickel compound or palladium compound and a cocatalyst exhibit high polymerization activity, the olefin polymers obtained using the catalysts are narrow in molecular weight distribution and thus do not necessarily have good molding properties (moldability). Improved catalysts comprising a nickel compound or palladium compound and cocatalyst which can produce olefin polymers of wide molecular distribution and excellent molding properties (moldability), without decreasing the high polymerization activity, have thus been desired.
Olefin polymers having excellent physical properties mentioned above are desired for use in a wide range of applications, and the desired physical properties differ according to the application. For example, in producing films from an olefin polymer, the olefin polymer requires excellent melt tension in order to prevent drawdown, etc., and the resulting films require good impact resistance, heat resistance, etc.
Furthermore, physical properties of olefin polymers are modified according to application. For example, propylene block copolymers, having both a crystalline polypropylene component and a rubber component, are known as materials that provide improvement in the impact resistance of crystalline polypropylenes. Japanese laid-open patent publication No. 4-337308 discloses a method of producing polypropylene block copolymers that exhibit an excellent balance of impact resistance and rigidity by the use of catalysts containing a silylene group bridge type metallocene compound as a catalytic component.
There are also known methods of forming polypropylene compositions by blending a rubber material such as non-crystalline polyethylene, non-crystalline or low-crystalline ethylene-propylene random copolymer, polyisobutylene or polybutadiene, as an impact resistance modifier, in crystalline polypropylene. For example, Japanese laid-open patent publication No. 5-202152 discloses a method of obtaining a polypropylene molding material of excellent low-temperature impact strength from a crystalline propylene polymer and a non-crystalline ethylene-propylene copolymer (EPR), wherein the EPR that is used is produced using a catalyst comprising a specific bridge type metallocene compound and aluminoxane.
Furthermore, the blending of atactic polypropylene as a modifier in polypropylene has been proposed, for example, in Japanese laid-open patent publication No. 6-263934.
There are also known methods in which an inorganic filler, such as talc, etc., is blended in a polypropylene composition to compensate for the lowering of rigidity that accompanies the addition of an impact resistance modifier.
In view of the prior art described above, the present inventors have examined catalysts that have high polymerization activity and enable the obtaining of olefin polymers of wide molecular weight distribution and excellent molding properties (moldability), and found that olefin polymers of wide molecular weight distribution can be obtained with a high polymerization activity when olefins are polymerized using a catalyst comprising the above-mentioned nickel compound or palladium compound, (i) a metallocene compound or (ii) a titanium catalyst component containing magnesium, titanium, and halogen as the essential components, and a cocatalyst such as aluminoxane, an ionic compound, etc.
The present inventors have furthermore examined olefin polymer compositions suitable as heat molding materials in view of the prior art described above and found that compositions formed from a non-crystalline olefin polymer which is produced using an olefin polymerization catalyst comprising the above-mentioned nickel compound or palladium compound and a cocatalyst, such as aluminoxane, an ionic compound, etc., and which has an intrinsic viscosity, glass transition temperature, and density within specific ranges, and another known olefin polymer, exhibit excellent rigidity and excellent impact resistance and are suitable as heat molding materials. The present inventors have also found that compositions formed from a crystalline olefin polymer which is produced using an olefin polymerization catalyst comprising the above-mentioned nickel compound or palladium compound and a cocatalyst, such as aluminoxane, an ionic compound, etc., and which has an intrinsic viscosity, glass transition temperature, and density within specific ranges, and another known olefin polymer, exhibit excellent mechanical properties, heat resistance, and molding properties (moldability) and are suitable as heat molding materials. The present invention has been accomplished on the basis of the above findings.